CCS part 2

Sebelum dilanjutken, perlu digaris bawahi bahwa tulisan ini merupakan kumpulan diskusi audio designer disebuah group ( lupa namanya ) sekitar thn 2004-2005.
Saya mah cuma alumni SD INPRES, ... nggak nyampe otaknya.
Jadi kalo bingung jangan tanya sama saya yah...
Judul diskusi wis kelalen, mungkin CCS vs Choke ?

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Detailed characteristics of a CCS:
1. A CCS can not swing above B+.

1.1 A CCS has a minimum voltage that can appear across it for it to
function or it will clip like an amp hitting the voltage rail. This minimum voltage can vary from a couple volts or tens of volts. For the coming example, lets call it 18 volts. This 18 volts has to be added to B+.

1.2 Half the peak to peak AC swing of the tube also needs to be added to
B+ to keep the CCS from clipping. (I like to add this voltage in assuming the tube is unloaded.) So if you are getting 400V pp out of the tube, B+ goes up another 200V for a total of 218V.

1.3 The B+ now has to have margin in it for line voltage variation. If B+ drops 50V because of low ac line, that is 50V less peak voltage the CCS can deliver, meaning the CCS will clip at a lower power out. This can be improved by using and "active load" CCS or cured by adding margin to B+ to cover line variations.

2. A CCS does not have a DCR. The closest thing to DCR is the minimum voltage drop needed for the CCS to work.

3. A CCS has an AC parallel resistance that is fairly flat with voltage
and frequency and is usually many times higher than the parallel resistance of an inductor. This AC resistance can be from 100's of kohm to >10,000 megohms.

4. The AC parallel capacitance of a CCS can be the same as an inductor or
so small the 6 inch wire to the CCS has more capacitance.

5. A CCS does not really have inductance. If it did, it would be infinite (megahenries). The effective impedance of some CCS will vary with voltage, but seldom with frequency. The amount depends on the design of the CCS.

6. A CCS delivers the same current all the time. That's why it is a CCS. A CCS can be designed to have a very slow turn on of the delivered current. This is something you can't do with an inductor.

7. CCS usually need heat sinking. NEVER believe the marketing rating for the power of a solid state CCS part. Transistor's power ratings are specified with the transistor attached to chilled, water cooled heat sinks that hold the surface of the transistor at 25C no matter how many watts are lost in the part.

7.1 Here's a problem with heat sinking CCS's. Many metal tab transistor
will arc over to the mounting screws (even with good insulating bushings and thermal mounting insulators) in the low hundreds of volts. If there is a burr on the heat sink, all bets are off. That burr is a failure just waiting to happen. (Don't use the blue silicon insulators, they tear so easily it isn't funny.) Use TO-220 fullpaks or TO-247 packages, these failure mostly go away.

7.2 Modern switch mode FETs can't be used in the linear region anywhere
near rated power. They internally have problems with current hogging. Fairchild Semiconductor has a article about this that I can't find back. Buy your
CCS FET based on smallest drain capacitance, highest voltage rating and in a minor part, the smallest Rtheta junction to case. This usually happens in the highest Rds-on part (4 ohm), not the lowest (0.8 ohm).

7.3 CCS usually have a "safe operating area" (SOA) that has to be watched. Bipolar devices have more SOA problems than FETs, but Bipolar devices have lower drain capacitance than FETs.

7.4 Remember, Silicon does not have a sense of humor. When it says 300V rating. At 301V peak instantaneous, the part can violently die. (The parts I have measured from on-semi had 15 to 20% margin at room temp.) When a tube says 300V rating, it means the DC bias point can be 300V and the ac peaks can go higher.

8. Most CCSs have very little or no magnetic pick up. Yes I can design one that would, but I'd have to try to do it.

9. Most CCS can have some capacitive coupling issues, but it is easy to
make the parasitic capacitance of a CCS 100 times or more better than an inductor.

10. Most CCS won't be sensitive to vibration, but with the wrong choice in parts they can be sensitive to vibration.

11. A well designed CCS will have an excellent transient and overload response. A poorly designed one won't. A CCS is an amplifier circuit in it's own right. Good ones make the music made by the amp sing, bad ones make it belch.

12. CCS can have current distortion. When measured in uA, you'd have to
Try to design one didn't work significantly better than an inductor. When measured in THD, they don't look as good. That is because the fundamental current change is almost zero! Example: 1 uA distortion (50%) on a 2 uA fundamental is bad when it comes to THD, but it works better than 150 uA (3%) distortion on a 5 mA fundamental.

Other notes using CCS

A. For a simple tube, you can CCS the plate or CCS the cathode. You can't CCS both. It is impossible to exactly match CCSs. So if you put a 1.0000 mA CCS on the plate and a 1.0001 mA CCS on the cathode, the bias point won't be right.

B. On a long tail pair, you can CCS two of the three connection, but not all three. You can CCS both plates or CCS one plate and the tail or just CCS the tail.

Warning. . .Inductor Distortion Soap Box:
The current distortion from an inductor must be specified in uA at each harmonic with a given drive voltage and frequency, not in THD. Most of the inductor's distortion is from the iron, not the air gap or other effects.
Increasing the air gap and keeping the copper the same (which drops the inductance) will make the THD look better, but the uA of third harmonic distortion does not significantly change. This is because the fundamental current flow has increased and the distortion components stayed about the same. The fallacy here is the fundamental current has increased causing the tube to makes more distortion because the load line is more elliptic etc but the tube still has the same amount of distortion current flowing in it from the inductor as it did before.

Now if the copper is redesigned so the inductance (and core material and size stays the same) but with a larger air gap, now the lower THD is good because the harmonic distortion in uA is now lower. The penalty for this change is a higher DCR and higher temperature rise.

== end of discussion ====

Not part 2

No one wants to die. Even people who want to go to heaven don't want to die to get there. - Steve Jobs

Day 11 .. CCS anyway part 1.

Day 11.

Amazing ... I've been here for 11 days, still lost in hole and still figure it out what am I doing here.
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CCS stands for a Constant Current Source. This means the current through
the device is constant no matter what the voltage across the device does.
(That is until you blow it up.)

A CCS can be made to deliver a constant current from DC on up to very high
frequencies or they can be made to look like a resistor at DC and turn to
constant current between 0.1 to 100 Hz (sort of like an inductor). Some
people call the ones that are a resistor at DC an "active load." I lump
them both under CCS's.

A big thing is a CCS on the plate of a tube requires a higher B+ than a
tube with an inductor on the plate. A CCS on the plate of a tube can operate
with the same B+ when the tube has resistor on the plate for bias.

In my book, a good CCS always sounds better than a resistor for bias. A
goodCCS usually sounds better than a typical inductor.

--- End of the simple explanation, on to the details. ---
--- Al, you may not be happy if you keep reading ;-] ---

Detailed characteristics of an inductor:
1. Can swing voltages above B+.

2. DC series resistance causes the B+ to need to be a bit higher to bias
up the tube.

3. Has AC parallel resistance (that varies with voltage and frequency)

4. Has AC parallel capacitance that can affect the load line at high
frequencies. This capacitance is fairly flat in value with voltage and
frequency.

5. Inductance (impedance = j * 2 * pi * frequency * L). The inductance
varies with voltage and frequency causing the impedance to vary with
voltage and frequency.

6. The inductance will vary with current and can drop to zero at too high
of a current.

7. An inductor usually has enough surface area that it cools itself
without needing added heat sinking.

8. An inductor suffers from magnetic coupling (both in to and out of the
part) with adjacent iron

9. An inductor can suffer from capacitive coupling (in and out again) with
adjacent parts and wiring.

10. An inductor can be sensitive to vibration.

11. Has a fairly well defined transient response

12. Generates current distortion that when multiplied by the plate
resistance of the tube, turns into a voltage distortion.


to be continue ....... mbuh kapan.

Meteran Reset

Meterannya kok re-set yach ? apa karena gratisan ?

Trafo untuk Power SS

Dari kiri ke kanan,

• Custom made, 10A cocok untuk bikin power Class A. Satu trafo cukup utk membuat 2 kanal ampli dengan daya hingga 2 x 20 watt. Sudah ditest dng tarikan arus 8A kontinyu dan trafonya cuma anget doank.
• Tamura 6A shielded, ada beberapa tap tegangan ttp yg inget cuma 27V-0-27V. High performance tranformer
• Trafo abal-abal 5A, no comment heheheee .... tapi cukup untuk bikin GC

The Art of LM317 - Coda

Selain dari nilai C yang optimal, ada 1 hal penting yang harus diperhatikan dalam mengoptimalkan LM317 yang seringkali terlewatkan yaitu membaca datasheet dari LM317.


Disana terdapat beberapa syarat supaya regulator ini bekerja optimal seperti penempatan R adj dan penggunaan C bypass pada C input.




Grounding yg optimal bisa dilihat dr ilustrasi berikut









Disini C3 , C4 dan load menggunakan jalur ground terpisah dng grounding C input ( C1 ) dan C adj. C2 sbg bypass dari C1 harus berada sedekat mungkin dng LM317.


Detail selengkapnya tentang C2 bisa dibaca di datasheet.





Juga dari graphic Fig 6 di datasheet dapat dilihat bahwa untuk mendapatkan regulasi yg baik, beda tegangan masukan dan keluaran harus berada antara 4V - 10V. Ini berati jika kita menginginkan output sebesar 12V, maka setidaknya tegangan yg masuk ke LM317 adalah 16V sampai 22V.









Selain itu, dari penelitian yg dilakukan oleh rekan2 DIYer yg memiliki test equipment yg memadai, arus yg dikonsumsi minimal adalah 10mA supaya regulasi dapat berjalan dengan baik. Jadi jika LM317 digunakan untuk mensuplai rangkaian yg hanya mengkonsumsi dibawah 10mA, maka hasilnya akan kurang memuaskan.



Blahhh ..... akhirnya kelar juga dah.




Tengkyu telah membaca

The Art of LM317 part 2

Part 2.


tanpa pake basa basi, berikut adalah sedikit modifikasi yang dilakukan pada rangkaian LM317



Perubahan yg dilakukan adalah hanya mengubah nilai C3 yaitu dari 470 uF ke 10 uF sementara yang lainnya tetap sama.

Hasilnya memang tidak membabat peak impedance yang ada tetapi menggeser ke frekuensi yang lebih tinggi yaitu dikisaran 60 KHz.








Sekarang bagaimana jika C3 adalah 47uF ? hasilnya adalah peak impedance hanya bergeser ke


kisaran 30 KHz





Dari hasil simulasi ini maka jika kita akan melakukan "tune-up" terhadap LM317, maka hasil yang signifikan akan diperoleh dengan mengutak-ngatik nilai C3. Dari pengalaman, sebaiknya C3 nilainya tdk lebih besar dari 22uF.

Dalam simulasi, perubahan nilai dari C4 ( sbg bypass C3 ) tidak menunjukan hasil yg signifikan tetapi pada kenyataannya akan mengubah suara highnya dan disini rekans bisa coba nilai antara 10 n - 100 n.

Dari hasil diskusi di beberapa forum DIY, LM317 justru kurang suka dng penggunaan elco berkualitas tinggi. Hasil maksimal justru diperoleh dengan menggunakan elco murmer yg high ESR. Tetapi tidak menutup kemungkinan justru rekan2 akan cocok dng karakter dari penggunaan elco yg audiophile approve

Mudah2an simulasi ini ada gunanya bagi rekans semua.

Pada kesempatan lain, saya akan coba melakukan simulasi "Tebak-tebak buah Manggis" yg merupakan hasil intepretasi dari penjelasan John Curl mengenai PSU dengan menggunakan LM317 .... kalo sempet heheeeee ......

Hasil tebak-tebakan ini sdh diaplikasikan pada preamp SS dng hasil yg mak nyusssss .....
Lebih baik dari preamp Aikido yg selama ini jadi andalan.
apakah ini karena PSUnya atau rangkaian pre SS nya ? entahlah ... yg jelas sy nggak mau ambil pusing, yg penting hasilnya mak nyusssss .....


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